Method of backing electrotype plates



.Fam 16, i934., R. T. HAINES METHOD OF BACKING ELECTROTYPE PLATES Filed NOV. 11, 1950 YOSWOJ GOOD A A 600D LOW BOY l Patented Jan. 16,` 1934 UNITED STATES PATENT OFFICE METHOD OF BACKIG ELECTROTYPE PLATES Rush T. Haines, Lansdowne, Pa., assgnor to Royal Electrotype Company, Philadelphia, Pa., a corporation of Pennsylvania Application November 11, 1930 Serial No. 494,917

8 Claims.

backed electrotype plate, so that a cutting tool by which the back is surfaced will meet a substantially uniform depth of cut at all times.

A further purpose is to fill in the hollows of a backed plate by flowed metal integrally attached' to the plate, as, for example, by soldering to the plate.

A further purpose is to heat an electrolytically backed plate to a point below its own fusion point but above the melting point of a backing material and to flow a backing material into intimate attached union with the backed plate for the purpose of rendering the plate initially level to facilitate a cutting operation upon the backing.

Further purposes will appear in the specification and in the claims.

My invention relates both to the method involved and to the intermediate product of manufacture in the plate produced.

I have preferred to illustrate my invention by but one. embodiment, selecting a form which is practical, highly efficient and generally desirable, and which at the same time well illustrates the principles involved.

Figure 1 is a front elevation of an electrotype plate which has not been backed.

Figure 2 is a rearv elevation of the plate of Figure 1. l

Figure 3 is a section of theplate of Figure 1 upon the line 3 3.

Figure 4 is a section corresponding generally to Figure 3 but showing the plate after it has been backed with copper.

Figure 5 is a section corresponding to Figure 3 but in which the backed plate has been levelled with material flowed into soldered union with the backing.

Figure 6 is a perspective view of the back of a plate which has been partly surfaced.

Figure 7 is a section corresponding to Figure 5 but in which the surfacing of the back has been completed.

In the drawing similar numerals indicate like parts.

A copper electrotype plate may be backed with copper, for example, electrolytically as disclosed in Walsh patent, No. 1,650,404, to produce a master plate, either positive or negative, of which the positive is a duplicate of the original engraved plate from which the electrotype was made.

The initial electrotype is straightened and is then backed. When the electrolytic deposit of such a master plate has been completed it is found that the back of the plate is quite uneven.

Unevenness of initial deposition of the metal of the electrotype and unevenness of the surface upon which it is deposited largely account for this fact. The front surface must be made the basis for straightening in the attempt to bring the entire plate within the plane of the printing surface. Inevitably the position of the nonprinting parts of this surface, such as 6, cannot be determined as well as the position of the printing face. Though these non-printing parts are intended to be plane, they may be convex, provided the convexity does not cause them to project to the plane of the printing face, or concave, without as good opportunity to judge of this fact and to straighten them accordingly as exists in the case of deformation of a portion of the printing surface.

Whatever the initial reason for unevenness of the surface which is coated the fact that the anode and cathode are nearer together at the high spots of the plate than at the low spots causes exaggeration of whatever initial unevenness may exist.

The reasons for the variation in the backed plate are diiTerently explained, but the fact remains that when the deposition of the backing metal has been completed the high and low spots upon the rear surface of the backed plate are quite noticeable.

When the uneven rear face of the backed electrotype is finished with a cutting tool the depth of the initial cut is relatively deeper at the high spots and is relatively shallower at the low spots, with the result that the cutting tool does not cut to an exact plane but tends relatively to dig into the plate or avoid the cut where the depth is deeper, 9

or to put up with and otherwise take care of a rear surface which is not even.

My invention is intended to overcome this difficulty by filling in the hollows of the back of the plate with molten metal united to the backing material of the plate so as to present a much more nearly uniform backed surface to the cutting tool than would otherwise be the case.

In carrying out my invention I back the plate to the condition shown in Figure 4, as in the practice, for example, of Walsh patent, No. 1,650,404, heat the back of the plate to a temperature higher than the melting point of the metal intended to be flowed into the hollows and add the metal in solid or molten condition.v

Before or after the heating I apply a flux in order that the added metal may be integrally attached to the backed plate.

The front and back of the same electrotype are shown in Figures 1 and 2, the showing in Figure 2 being that of the unbacked electrotype.

In Figure 3 the hollows at the back (corresponding to the printing front surfaces) are shown at 7 and the relatively high spots at 8. The electrolytically deposited backing is shown at 9, Figure 4, the flux at 10 and the molten metal flowed in is shown at 11. When the molten metal (whether initially solid 0r not) has united with the back of the plate the flux disappears (Figure 5).

It will of course be understoodthat the plate will be face downward, substantially horizontal, when the molten metal 11 is applied.

Except that the electrolytically deposited backing metal cannot be heated so hot as to injure it or risk melting it, the melting point of the molten metal 11 is not very material, and the iiux used can obviously be any flux which will serve the purpose to unite the backing metal and the filling metal. In practice I find sterotype metal, or tin, or type metal well suited for the purpose of levelling copper plates, and can use any uX which is suitable for uniting them to the copper for the backing. Various metals melting at relatively low temperatures are well known in the printing art, and any of these can be used which will unite well with the copper.

A convenient way of adding the filling metal is to heat the backed electrotype, painting. it with ux before or preferably after the heating, approximately level it, and cover it with as many sheets of foil of the character desired, as are required to fill the hollows and level the plate to the condition shown in Figure 5. Tinfoil will serve the purpose well.

Though copper and the filling metal will not cut exactly the same during the surfacing operation, the presence of the filling metal or alloy makes the operation of the cutting tool very much more nearly uniform than would be the case if the filling metal were not present. Sweating the lling metal or alloy into the hollows as indicated is my preferred method of supplying it to the plate but the metal can be supplied in molten form. The backed plate should also be heated to secure good union between the two metals.

As is well known the hollows between the high spots of the electrotype are not actually very deep but minute differences in thickness make a great deal of difference in the performance of the electrotype plate and become objectionable correspondingly. For purposes of illustration the differences in thickness of the plates have been greatly exaggerated.

InFigure 6 I show a plate lying face downward, having been partially surfaced by the tool l2. The portion 13 has been surfaced down to the thickness seen in the section of the finished plate, Figure 7.

I will preferably make the surfacing cut deep enough to remove entirely the metal 11 flowed into the hollows at the back, but it would not be necessarily undesirable to leave metal 11 in unusually deep cavities, removing however the great bulk of this metal.

In view of my invention and disclosure variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art, to obtain part or all of the benefits of my invention without copying the structure shown, and I, therefore, claim all such in so far as they fall within the reasonable spirit and scope of my invention.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. The method of backing a printing plate, which consists in depositing backing metal upon the nonprinting face of the plate, in heating and iluxing the plate, in flowing metal or alloy into union with the nonprinting face of the plate to fill up the hollows of the nonprinting face of the plate and in cutting from the nonprinting face of the plate until the plate is of such thickness that the electrodeposited backing metal is exposed over a portion of the nonprinting face.

2. The method of backing a printing plate, which consists in electrodepositing backing metal upon the nonprinting face of the plate, in approximately levelling the printing face of the plate, in heating the plate, in sweating metal or alloy into soldered union with the nonprinting face of the plate to fill the hollows of the plate and in cutting from the nonprinting face of the plate until the plate is of such thickness that the electrodeposited backing metal is exposed over a portion of the nonprinting face.

3. The method of backing a printing plate,

which consists in electrodepositing a metal high in copper upon the nonprinting face of the plate, in approximately levelling the plate by the printing face of the plate, in sweating a lead alloy into soldered union with the nonprinting face of the plate to fill the hollows of the plate and in cutting from the nonprinting face of the plate until the plate is of such thickness that the metal high in copper is exposed over a portion of the nonprinting face of the plate.

4. The method of backing a printing plate, which consists in electrodepositing backing metal -upon the Vnonprinting face of the plate, in filling the hollows of the nonprinting face of the plate with a supporting metal or alloy applied by heat and in cutting the nonprinting face of the plate which has been made uniform by the filling material, entirely removing the supporting metal or alloy by the cutting.

5. The method of surfacing the back of a plate having relative high spots and hollows, which consists in filling the hollows with a supporting material and cutting the plate as thus filled, to a depth suicient to entirely remove the supporting material.

6. The method of backing a printing plate, which consists in electrodepositing backing metal upon the nonprinting face of the plate, in casting metal in the depressions of the backing metal and in cutting from the nonprinting face of the 'plate to a depth suflicient to remove. electroV 8. The method of backing an electrotype made from an alloy high in copper, Whchconsists in electrodepositing copper backing upon the nonprinting face of the electrotype, in approximately leveling the plate by its printing face, in heating the plate, in sweating a lead alloy into soldered union with the back of the plate to ll the hollows of the plate and in roughing away the lead alloy and the high points of the copper backing.

RUSH T. HAINES. 

